1. Field of the Disclosure
The present disclosure relates to compositions for use in refrigeration systems wherein the composition comprises tetrafluoropropenes and difluoromethane. The compositions of the present invention are useful in methods for producing cooling, methods for replacing refrigerants and air conditioning and heat pump apparatus.
2. Description of Related Art
The refrigeration industry has been working for the past few decades to find replacement refrigerants for the ozone-depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) being phased out as a result of the Montreal Protocol. The solution for most refrigerant producers has been the commercialization of hydrofluorocarbon (HFC) refrigerants. The new HFC refrigerants, HFC-134a being the most widely used at this time, have zero ozone depletion potential and thus are not affected by the current regulatory phase out as a result of the Montreal Protocol.
Further environmental regulations may ultimately cause global phase out of certain HFC refrigerants. Currently, industry is facing regulations relating to global warming potential (GWP) for refrigerants used in mobile air-conditioning. Should the regulations be more broadly applied in the future, for instance for stationary air conditioning and refrigeration systems, an even greater need will be felt for refrigerants that can be used in all areas of the refrigeration and air-conditioning industry. Uncertainty as to the ultimate regulatory requirements relative to GWP, have forced the industry to consider multiple candidate compounds and mixtures.
Previously proposed replacement refrigerants for HFC refrigerants and refrigerant blends include HFC-152a, pure hydrocarbons, such as butane or propane, or “natural” refrigerants such as CO2. Each of these suggested replacements has problems including toxicity, flammability, low energy efficiency, or requires major equipment design modifications. New replacements are also being proposed for HCFC-22, R-134a, R-404A, R-507A, R-407C and R-410A, among others.
Uncertainty as to what regulatory requirements relative to GWP will ultimately be adopted have forced the industry to consider multiple candidate compounds and mixtures that balance the need for low GWP, an occupational exposure limit (OEL) greater than 400 ppm, and existing system performance parameters.
In particular, there is a need for refrigerants with OEL greater than 400 ppm, both as formulated and after a leak.